Effects of steel fibers on the strength of reinforced concrete members subjected to impact loading

TUBITAK - The Scientific and Technological Research Council of Türkiye


Reinforced concrete structures may be subjected to impact loads due to various reasons in their lifetimes. Accidents in industrial buildings, vehicle collisions to railway and highway bridges and barriers, rock falls on road structures, collisions on sea structures such as oil platforms and piers are examples of cases in which structures are subjected to impact loads. Such impact loads may threaten the structural safety and cause structural damage and collapses.

This project is aimed towards investigating the effects of use of steel fibers for increasing the impact capacity of reinforced concrete structures. For this purpose, 16 slab specimens of size 2.15x2.15x0.15 m and 16 beam specimens of size 0.250x0.150x2 m were cast using 0%, 0.5%, 1% and 1.5% steel fibers and tested under static and impact loads. Impact loads were applied by the free fall of varying drop weights on the midpoints of the beams and slabs, while the accelerations, support reactions, rebar strains and deformations were recorded with a high-speed data acquisition system. Static tests were also performed via a hydraulic jack, aiming to see the relation between the static behavior and the impact behavior. In these experiments, it was observed that adding steel fibers increased the impact capacity of both slabs and beams significantly. Specimens with steel fibers resisted more impact loads with higher weight impact weights without losing the integrity of the member compared to the specimens without steel fibers. Specimens with steel fibers suffered minor damage where specimens without steel fibers were heavily damaged. Steel fibers also changed the failure mode of the specimens. For example, specimens failing under brittle shear under static loads failed under flexure when steel fibers were added, increasing the energy absorption capacity of the member. In this study, it was concluded that steel fibers can significantly increase the structural safety of the structures prone to impact loads. 


Impact testing
Testing of fiber reinforced concrete beams under impact loads
Impact testing
Failure of a fiber reinforced concrete beam after impact
Impact Testing
Bottom of a fiber reinforced concrete slab tested under impact loads
Impact Testing
Instrumentation in beam impact tests

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